Automatic back hoe control system



p 1967 J. A. CAYWOOD ETAL 3,339,763

AUTOMATIC BACK HOE CONTROL SYSTEM 5 Sheets-$heet 1 Original Filed Aug.19 1965 wm SE28 E859 INVENTORS ERNEST C. FITCH, JR DEAN M. DEMOSS RONALDF. OSBORN JAMES O MATOUS 7 JAMES A. CAYWOOD V ATTORNEYS Sept- 5, 1967 J.A. CAYWOOD ETAL 3,339,763

AUTOMATIC BACK HOE CONTROL SYSTEM Original Filed Aug. 19, 1965 5Sheets-Sheet z? TO TANK TO HYDRAULIC POWER PRESSURE SOURCE CURL JACKLIFT JACK MANUAL VALVES CROWD JACK INVENTORS ERNESTC. FITCH, JR DEAN M.DeMOSS RONALD E OSBORN JAMES O. MATOUS JAMES A. CAYWOOD ATTORNEYS 33 TOHYDRAULIC SIGNAL PRESSURE SOURCE P 5, 1967 I J. A. CAYWOOD ETAL3,339,763

AUTOMATIC BA JK HOE CONTROL SYSTEM Original Filed Aug. 19, 1965 5Sheets-Sheet 3 -m1- HII I a g I 6 0 H2 5 (BF IN VE N TORS DEA/V M DeMOSSRONALD E OSBORN JAMES O. MATOUS JAMES A. CAYWOOD -S- lvL ma ATTORNEYSERNEST C. FITCH, JR

p 1967 J. A. CAYWOOD ETAL 3,339,763

AUTOMATIC BACK HOE CONTROL SYSTEM 5 Sheets-Sheet 4 Original Filed Aug.19, 1965 wutDOm mtbmmmtl 41205 UIDQQAKI Oh $3 t3 mm E E: 298m EmINVENTORS ERNEST C. FITCH JR DEAN M. DeMOS RONALD F. OSBORN JAMES O.MATOUS JAMES A. CAYWOOD mm VN X03 wztxm HIDE X03 95km kil v63 kucq v63ESQ r63 930mb ATTORNEYS Patented Sept. 5, 1967 AUTOMATIC BACK HOECONTROL SYSTEM James A. Caywood, Birmingham, Mich, and Dean M.

De Moss, Ernest C. Fitch, Jr., Ronald F. Osborn, and

James O. Matous, Stillwater, Okla., assignors to Oklahoma StateUniversity of Agriculture & Applied Science, Stillwater, Okla., acorporation of Oklahoma Continuation of application Ser. No. 480,860,Aug. 19,

1965. This application Oct. 14, 1966, Ser. No. 587,385

22 Claims. (Cl. 214-138) This is a continuation of application Ser. No.480,860 filed Aug. 19, 1965, now abandoned.

This invention relates to a backhoe, and more particularly to ahydraulically actuated backhoe. Still more particularly, this inventionrelates to an automatic hydraulic backhoe control system which may beplaced in parallel arrangement with a manually operated control system.

Backhoe units generally consist of a series of sequentiallylongitudinally pivotally attached arms mounted on a tractor chassis atthe extremity of which arms is located a bucket or digging attachmentoriented to perform its digging operation by movement toward the tractorunit. The movement of the arms and bucket are generally hydraulicallycontrolled. The name backhoe is given units mounted in this manner sincethey are normally mounted at the rear of the tractor unit and performthe digging or trenching operation toward the tractor, the direction inwhich the tractor is positioned to travel. By being positioned in thismanner, the backhoe is capable of digging a narrow trench while thetractor itself proceeds ahead of the digging operation on solid ground.The backhoe units find their most valuable application in the digging oftrenches for the laying of cables, pipelines, sewage lines, and soforth.

The description of this invention will be given by reference to a typeof tractor mounted backhoe unit in common usage, however, it isunderstood that the invention relates to, and the word backhoe as usedherein refers to, any type of digging machine utilizing a bucket on theend of a hydraulically actuated hinged boom.

The hydraulically operated backhoes in present use require the constantattention of the operator to the various functions. The operator mustattentively operate numerous levers to carry out the necessary sequenceof operations. Throughout each step of the digging process the operatormust make continual decisions as to the necessary attitudes andmovements of the components of the backhoe, and pull or push levers atthe proper time to direct the digging cycles. For these reasonsconsiderable timeis required to train a skillful backhoe operator. Evenafter the skill is acquired, the work is demanding and tiring, requiringcontinuous mental and physical alertness to maintain maximum diggingrates. 5 The primary object of this invention is to provide a hydraulicsystem which liberates the human operator from most of the intricatehand and finger manipulations presently required to operate a backhoemachine.

Another object of this invention is to provide an automatichydraulically operated backhoe which can be operated with a minimumamount of attention of the operator.

Another object of this invention is to provide an automatic backhoehydraulic circuit which may be placed in parallel arrangement with aconventional manually operated hydraulic backhoe system.

Another object of this invention is to provide an automatic backhoehydraulic circuit in which the digging cycle functions and/or theretraction cycle functions can be initiated by the operation of a singlelever.

Other objects and advantages as well as a full understanding of theinvention will be had from the following description and claims, takenin conjunction with the accompanying drawings, in which:

FIGURE 1 is a side elevational view of a tractor and backhoe machine towhich the automatic hydraulic control system of this invention has beenapplied.

FIGURE 2 is a pictoral flow diagram of the basic digging cycle hydrauliccontrol system of this invention.

FIGURE 3 is a sectional view through the line 33 of FIGURE 1 showing thecylinders controlling the lateral or horizontal swing of the backhoeboom.

FIGURE 4 is a partial enlarged side elevational view showing the manualcrowd lever and related control valve.

FIGURE 5 is a partial cross-sectional view through the line 55 of FIGURE1 showing the swing detection cams and swing detection valves.

FIGURE 6 is an enlarged elevated view of the lift attitude cam andvalve.

FIGURE 7 is a composite schematic diagram of the automatic backhoehydraulic circuit of this invention providing automatic digging andretraction cycles.

FIGURE 8 is a composite schematic diagram of the automatic backhoehydraulic circuit of this invention providing a completely automaticfull cycle.

The automatic hydraulic control system of this invention is adaptable tooperate in parallel with a manually operated control system so that theoperator of the backhoe may choose either manually or automatically tooperate the machine and may switch from manual to automatic operationand vice versa at any stage of the operation. Manual operation of thebackhoe unit requires the operator to dexteriously position the variouscomponents of the backhoe by manipulation of levers which operate valvesto admit hydraulic fluid under pressure to jacks which control themovement of the machine components. This invention provides an automaticcontrol system in which the elements of the backhoe machine areautomatically actuated, relieving the operator of substantially all theeffort and judgment normally required.

This invention may be described as an automatic hydraulic control systemfor a backhoe machine, or a backhoe machine including automatichydraulic control systems. More particularly, but not by way oflimitation, the invention may be described as a backhoe machine having atractor, a boom consisting of a lift arm pivoted at one end to thetractor, a crowd arm pivoted at one to the other end of the lift arm,and a bucket pivoted to the other end of the crowd arm, a double actinghydraulic jack, termed a lift jack, pivotally affixed at one end to thetractor and at the. other end to the lift arm whereby the lift arm ispivotally positioned relative to the tractor in a vertical plane, thelift arm being raised to a decreased digging attitude and lowered to anincreased digging attitude, a hydraulic jack, termed a crowd jack,pivotally afiixed at one end to the lift arm and at the other end to thecrowd arm whereby the crowd arm is pivotally positioned in a verticalplane relative to the lift arm, the crowd arm being moved inwardly toincreased digging attitude or outwardly to decreased digging attitude, adouble acting hydraulic jack, termed a curl jack, pivotally affixed atone end to the crowd arm and at the other end to the bucket whereby thebucket is pivotally positioned in a vertical plane relative to the crowdarm, the bucket being pivoted inward to decreased digging attitude oroutwardly to an increased digging attitude, a source of hydraulic fluidpressure carried by the tractor, a manual lift valve controlling fluidcommunication between the pressure source and the lift jack, ahydraulically operated valve, termed a lift valve, controlling fluidpressure to the lift jack to move the lift jack to increased ordecreased digging attitude, a hydraulically operated curl valvecontrolling hydraulic fluid flow to the curl jack to pivot the bucket toincreased or decreased digging attitude, an overload signal valve incommunication with and sensitive to the hydraulic pressure in the crowdjack and providing a signal output when the hydraulic pressure in thecrowd jack moving the crowd arm to increased digging attitude exceeds apreselected level, and means responsive to the overload signal valve ofactuating the curl power valve and thereby the curl jack to move thebucket to decreased digging attitude when overload condition is detectedin the crowd jack. In further particular, the backhoe machine of thisinvention includes, in addition to the above described elements, anoverload signal valve detecting pressure in the curl jack as the curljack is moved to decreased digging attitude and including meansresponsive to overload detection by both the crowd overload signal valveand the curl overload signal valve of actuating the lift jack powervalve to pivot the lift arm to decreased digging attitude so that, asthe backhoe is operated and the crowd arm is moving inwardly towards thetractor in the digging operation, lift jack and curl jack areautomatically controlled to, accomplish the digging cycle. In a stillfurther definition of thisinvention, in addition to the above describedelements, the backhoe machine includes means responsive to the hydraulicpressure in the crowd jack as hydraulic pressure is applied to the jackto move the arm outward in the initial stages of the retraction cycle.including means of actuating the curl jack power valve to pivot thebucket inwardly whereby the bucket is pivoted inwardly as the crowd ismoved out to automatically maintain the bucket in substantially levelposition as the crowd arm is moved out during the boom retraction cycle.In still further particularity, the invention includes, in addition tothe above described elements, means of automatically swinging the boomarm in a horizontal plane. to One side, automatically dumping thebucket, and automatically returning the boom to the proper position forthe initiation of a new digging cycle. 7 The expression increaseddigging attitude with reference to the lift arm, the crowd arm and thebucket means the change in attitude which would result in fully fillingthe bucket quickly under ideal conditions, and particularly means thelift arm is pivoted downwardly, the crowd arm is pivoted towards thetractor and the bucket pivoted outward. In like manner the expressiondecreased digging attitude means the lift arm is pivoted upwardly, thecrowd arm is pivoted away from the tractor, and the bucket is pivotedinwardly. In other words, the expressions increased digging attitude anddecreased digging attitude are used only to indicate direction ofpivotation of the elements of the backhoe and are not synonymous withfaster, slower, better or worse instantaneous digging effectiveness.

Referring now to the drawings and first to FIGURE 1, a backhoe machineis shown consisting of the basic components of a tractor 10 havingmounted at the rear thereof a boom, indicated generally by the numeral12. Typically, a backhoe tractor 10 is provided with a front end loader,generally indicated by the numeral 14, which has no part in theinvention.

The boom 12 consists of six basic components. These are:

A lift arm 16 having ends 16A and 16B pivoted at end 16A to the tractor10;

A crowd arm 18 having ends 18A and 18B pivoted at end 18A to end 16B ofthe lift arm;

A bucket 20 pivoted to the end 18B of the crowd arm 18;

A' double acting hydraulic jack 22 pivotally connected at one end to thetractor 10 and at the other end to the lift arm 16 whereby the lift arm16 is pivoted in a vertical plane, this jack being referred to as thelift jack;

A double acting hydraulic jack 24 pivotally connected at one end to thelift arm 16 and at the other end to crowd arm 18 whereby the crowd arm18 is pivoted in a vertical plane relative to the lift arm 16, this jackbeing referred to as the crowd jack; and

A double acting hydraulic jack 26 pivotally connected at one end to thecrowd arm 18 and at the other end to bucket 20 whereby the bucket ispivoted in a vertical plane relative to the crowd arm, this jack beingreferred to as the curl jack.

All of the components of the backhoe machine described to this point aremore or less standard in the industry. The boom 12 is controlled byhydraulic fluid pressure directed into the jacks 22, 24 and 26, thefluid flow being normally directed by an operator manipulating manualvalves, generally indicated by the numeral 28. Typically, there are fourlevers operating the manual valve 28, each of which basically consistsof an opencenter double position valve wherein the valve pushedoutwardly conducts fluid to cause a jack to operate in one direction andWhen pulled inwardly conducts fluid flow to cause a jack to move in theopposite direction, with the center position being the off or no-flowposition.

This invention consists essentially of applying to the typicalhydraulically operated tractor backhoe unit described to this point ahydraulic control system whereby substantially all of the manualmanipulation of the valves 28 is replaced by automatically controlledsystems.

Referring now to FIGURE 2, a pictoral flowdiagram is shown of the basichydraulic circuit of the invention constituting the first phase of theinvention, wherein the digging cycle of the backhoe boom isautomatically controlled.

Positioned in parallel with the curl manual valve 28C is a hydraulicallyoperated four-way blocked center valve 30, termed a curl power valve.This .valve controls bydraulic fluid pressure to the curl jack 26paralleling op-. eration of the manual valve. The curl power valve is athree-position valve hydraulically controlled by fluid pressure inconduit 32.

In like manner, a hydraulic operated four-way blocked center valve 34parallels the lift manual valve 28B and is controlledby hydraulic fluidthrough conduit 36. This valve is termed the lift power valve 34.

The operation of the hydraulic circuit of FIGURE 2 is initiated when theboom 12 (see FIGURE 1) is positioned in an extended attitude with thelift arm 16 low, the crowd arm 18 extended outwardly substantiallyhorizontally, and the bucket 20 extended outwardly in the maximumdigging attitude.- To initiate digging to fill the bucket 20, theoperator pulls the manual crowd valve 28A towards him which causeshydraulic fluid pressure to flow into the crowd jack 24 through conduit38. This starts a retraction of the crowd arm 18 moving the bucket 20into the earth. Normally the operator must make continuous manualadjustments as the crowd arm is moved in, raising and lowering the boomby hydraulically controlling the lift jack and correcting the attitudeof bucket 20 so that the system will not be overloaded but'at the sametime maximum. digging will be provided so that ideally at the end of thedigging cycle, a full bucket of earth is obtained. In the automaticcontrol system of FIGURE 2, these continuous manual adjustments areautomatically achieved. An overload signal valve 40 is connected toconduit 38 and is sensitive to the hydraulic pressure in the crowd jack24. As hydraulic pressure in the crowd jack increases, the valve 40 isactuated pro viding a hydraulic crowd overload signal S1 in conduit 32.The overload signal valve 40 is supplied with a hyhydraulic signalpressure by conduit 42. The source of hydraulic signal pressure may beprovided, such as by means of a pressure reducing valve or thelike (notshown), connected to the tractor hydraulic pressure sys-. tem source.Usually the hydraulic signal pressure source is at a lower pressure thanthe main hydraulic pressure source of the machine and for successfuloperation of the automatic controlled backhoe machine of this invention,such hydraulic pressure signal source should be at a substantiallyconstant level.

In communication with the conduit 44 by which hydraulic fluid -isconducted to the in port of curl jack 26 is a second overload signalvalve 46, termed a curl overload signal valve. When overload isexperienced in the conduit 44, the curl overload signal valve 46provides a hydraulic signal S3 at conduit 48. A pilot operated checkvalve 50 is controlled by signal S3 in conduit 48 as previouslyindicated. A check valve 51 is provided between conduits 36 and 48 sothat signal S4 is relieved when conduit 48 is tanked by overload signalvalve 46.

A pilot operated check valve 52 is interposed in conduit 38 so that thepressure which the crowd overload signal valve 40 receives from thecrowd jack 24 is isolated from the rest of the system. In this way thepressure monitored by the crowd overload signal valve 40 is not affectedby other devices in the system. In like manner, check valve 54 isolatesthe signal received by the curl overload signal valve 46. Check valves56 and 58 serve as low pass filters for the overload signal valves 40and 46.

Operation of automatic digging cycle control system As previouslyindicated, FIGURE 2 illustrated the first basic portion of the automaticbackhoe hydraulic system of this invention whereby automatic diggingcycle control is obtained. To illustrate the operation of this circuitit will be assumed that the backhoe boom 12 (as shown in FIGURE 1) ispositioned ready to begin the digging cycle with the lift arm 16 inrelatively low position, the crowd arm 18 extended and the bucket 20extending in the out or maximum digging position. To initiate thedigging cycle, the operator pulls the lever of manual crowd valve 28Atowards him which causes hydraulic fluid to fiow through conduit 38 tothe hydraulic jack 24 moving the crowd arm inwardly towards the tractor.This causes the bucket 20 to dig into the earth and start the digging orfilling of the bucket. The inward movement of the crowd arm willcontinue with the bucket in the maximum digging attitude until anoverload condition is reached. This overload will cause pressure buildupin the crowd jack 24 and in conduit 38. This pressure is monitored bycrowd overload signal valve causing the hydraulic signal S1 in conduit32. This hydraulic signal is applied to curl power valve 30 pivoting itto cause hydraulic fluid flow through conduit 44 to curl jack 26.Actuation of curl jack 26 causes inward pivotation of the bucket 20 to adecreased digging attitude, that is, the bucket is not inclined to digas deeply into the earth. At this point in the operation, two,conditions may occur. The first is that such inward pivotation of thebucket 20 relieves the overload condition. If this occurs the hydraulicpressure in conduit 38 drops causing the closure of crowd overloadsignal valve 40. The crowd jack continues to actuate the crowd arminwardly. Relief of the crowd overload removes the overload signal S1 inconduit 32 causing the curl power, valve 30 to move back to centerposition so that no further adjustment is made in the bucket attitude.The crowd jack will continue to actuate by fluid flow through conduit 38until further action.

The second possible occurrence when overload condition is detected incrowd jack 24 and curl jack 26 is actuated by signal S1 is that the curljack itself will become overloaded. This occurs as pressure build-up inconduit 44 increases. Such pressure build-up is detected by the curloverload signal valve 46 providing a curl overload hydraulic signal S3in conduit 48. When such overload signal is detected, the pilot operatedcheck valve 50 is actuated providing an open path between conduit 32 andconduit 36 which connects with the lift power valve 34. The pilotoperated check valve 50 and check valve 51 functions as an and controlcircuit, that is, a hydraulic signal S4 is provided in conduit 36 onlywhen both signals S1 and S3 are provided in conduits 32 and 48. When asignal S4 is applied in conduit 36, which occurs only when both thecrowd and curl jacks 24 and 26 are overloaded, the lift power valve 34is pivoted to cause hydraulic fluid 6 flowing in conduit 62 actuatinglift jack 22 to pivot the lift arm 16 in an upward or decreased diggingattitude. As the lift arm 16 is pivoted upward, the bucket 20 is movedto decreased contact with the earth which will immediately result ineither the crowd, the curl, or both the crowd and curl jack overloadconditions being relieved. When this occurs the overload signal S4 inconduit 36 is removed terminating any further upward pivotation of liftarm 16.

As the boom continues to move inwardly towards the tractor by the inwardpivotation of crowd arm 18, the hydraulic control system of thisinvention continually monitors the pressure condition and adjusts theattitude of the bucket and lift arm to relieve overload conditions. Suchoverload conditions are relieved rapidly insuring maximum diggingefliciency. By the application of the automatic control system of FIGURE2, the operator accomplishes a complete digging cycle by merely manuallymoving the crowd valve 28A to initiate the inward pivotation of thecrowd arm. The operator does not haveto utilize the manual lift or curlvalves 28B and 28C since all necessary adjustments in the curl and liftjacks are made by the control system of the invention.

Automatic digging and retraction control system Referring to FIGURE 1, alift position valve 64 is shown supported to the tractor and iscontrolled by a lift position cam 66. This is best shown in the enlargedview of FIGURE 6. The cam 66 is afiixed to the end 16A of the lift arm16. The lift position valve '64 which is controlled by cam 66 is a camoperated four-way three positioned spring offset center bypass valve,the purpose and function of which will be described subsequently.

Referring again to FIGURE 1, an automatic retraction valve 68 is shownsupported to the tractor and is actuated "by the lever of manual crowdvalve 28A. This is best shown in the enlarged view of FIGURE 4. Theautomatic retraction valve 68 is supported to the tractor 10 in closerelationship to a crowd lever 70, the lever which operates the crowdvalve 28A. The automatic retraction valve 68 is a three-way two positionspring biased cam actuated valve. The valve is shown in the springposition in FIG- URE 7. When the crowd lever 70 (see FIGURE 4) is ineither the neutral position or in the crowd in position the valve 68 isin the spring position shown and is in the cam. position when the crowdlever 70 is in the crowd out position.

A manual-automatic selection valve 72 is provided whereby either manualor automatic retraction of the boom is selectable. In FIGURE 7 the valveis shown in the automatic position. Other than the lift arm positionvalve 64, the automatic retraction valve 68, the swing direction valve96, and the selection valve 72, all of the other valves making up theautomatic digging and retraction cycle sys-, tem of this invention asshown in FIGURE 7 are hydraulically controlled.

All of the valves as previously described with reference to FIGURE 2providing the automatic digging cycle are included in the automaticdigging and retraction cycle system of FIGURE 7, however, the functionof lift power valve 34 and check valves 54 and '58 are changed somewhatin type and function as indicated in FIGURE 7 and as will besubsequently described. In addition to the components of the automaticdigging cycle system of FIGURE 2, the system of FIGURE 7 provides thenecessary ele-, ments to achieve both automatic digging and retractioncycles of the boom. Upon completion of the digging cycle, theretractioncycle. is initiated by the operator switching the manual crowd valve 28Ato the crowd out position which is done by merely pushing the crowdlever 70 outwardly. This provides hydraulic pressure in conduit 74connecting to the crowd jack 24 causing the crowd arm to start movingoutwardly. Whenthe crowd lever 70 is moved to the out position,automatic retraction valve 68 is moved to the camposition so thathydraulic fluid pressure in conduit 74 is communicated to conduit76. Thehydraulic pressure in the crowd jack 24 is therefore reflected in theconduits 76 and is monitored by a low pressure overload signal valve 78and a high pressure signal valve 80. When overload pressure in the crowdjack out conduit 74 is detected by the low pressure overload signalvalve 78, a hydraulic signal S7 is imposed through conduit 82 to a curlsignal shuttle valve 84. This signal passes through valve 84 to curlpower valve 30 actuating it and causing fluid flow to curl jack 26resulting in inward pivotation of the bucket for purposes to bedescribed subsequently. The curl signal shuttle valve 84 functions as anor valve, that is, it permits actuation of the curl power valve 30 byeither signal S1 or signal S7.

As previously mentioned, the hydraulic pressure in crowd jack outconduit 74 and thereby in conduit 76 is also monitored by the highpressure overload signal valve 80. This valve 80 is set so that only thepressure build up which is experienced when the crowd jack 24 reachesthe outer limits of its travel will the valve be actuated. When it isactuated, a hydraulic signal S8 is provided in conduits 86. The pressuresignal S8 serves two functions, the first being to actuate a hydrauliccurl signal block valve 88 which blocks signal S7 thereby blocking anyfurther inward pivotation of the curl jack 26. The second function ofthe hydraulic signal S8 in conduits 86 is to begin the initiation of theswing of the backhoe boom to the left or the right of the tractor sothat dirt accumulation in the bucket during the digging cycle can beemptied.

The swinging of the boom to the left or right in a horizontal plane toafford dumping of earth removed by the backhoe is accomplished by a lefthydraulic swinging jack 90 and a right hydraulic swinging jack 92. Theseswinging jacks 90 and 92 are controlled by means of manual swing valve28D. Typically such a valve is arranged so that the operator can bypushing a single valve lever away from him cause the boom to swing inone direction and by pulling it towards him cause the boom to swing inthe opposite direction. In parallel with the manual swing valve 28D is ahydraulically operated swing power valve 94. This is a pilot operatedfour-way blocked center valve. A manually operated swing directionselection valve 96 directs the hydraulic operating signal into the swingower valve '94 so that the direction which the boom will swing ismanually selectable. interposed between the conduit 86 which carrieshydraulic signal S8 are two swing blocking valves, a low lift armblocking valve '98 and a high lift arm blocking valve 100. Blockingvalve 98 is controlled by signal 89 and blocking valve 100 by signal S6.If the lift arm 16 (FIGURES 1 and 6) is too high, the lift positionvalve 64 provides a hydraulic signal S6 in conduit 102 which actuatesthe high lift arm blocking valve 100, thereby blocking signal S8. If thelift arm 16 is too low, the lift position valve 64 provides a hydraulicsignal S9 in conduit 104 which actuates the low lift arm blocking valve98'to block the signal S8. Conduit 102 which carries the high lift armsignal S6 from valve 64 also connects to the lift power valve 34 so thatwith signal S6 present valve 34 is actuated to lower the lift arm. Whensignal S9 is provided in conduit 104, it is communicated through a liftsignal shuttle valve 106 to conduit 60 and becomes signal S to actuatelift power valve 34 to cause hydraulic fluid to flow from conduit 42 tothe lift jack 22 to raise the lift arm. Thus the lift signal shuttlevalve 106 is in effect an or valve in that the lift power valve isactuated by either signal S4 -or $9.

Automatic retraction cycle Assuming the automatic backhoe machine ofthis invention has completed a digging cycle as previously described,all the operator has to do to cause the machine to automatically performthe retraction cycle is to move the crowd lever 70 (see FIGURE 4) to thecrowd out position. This has two results. First, the manual crowd valve28A is moved to the out position so that hydraulic fluid pressure issupplied to conduit 74 which connects with the crowd jack 24 so thatthecrowd arm is pivoted outwardly. Second, the automatic retraction valve68 is actuated. This provides hydraulic fluid in conduit 76. Thepressure in conduits 76 is the reflection of the pressure in the crowdjack 24 and is monitored by the low pressure overload signal valve 78and the high pressure overload signal valve 80. The purpose of the lowpressure overload signal valve 78 is to maintain the bucket 20 (seeFIGURE 1) in a substantially level position as the crowd arm is pivotedoutwardly to prevent the dirt which has been forced into the bucketduring the digging cycle from spilling out. As

the crowd arm 18 pivots outwardly the hydraulic pressure required in thecrowd jack 24 increases. This pressure increase is detected by the lowpressure overload signal valve 78 which, when actuated, applies ahydraulic signal S7 by way of conduit 82 through the curl signal blockvalve 88 and the curl signal shuttle valve 84 to actuate the curl powervalve 30, causing the curl jack 26 to pivot the bucket 20 towards theinward position. As the arm 18 pivots further outwardly, the pressure incrowd jack 24 increases and by the continuous monitoring of thepressuring by the overload signal valve 78, the curl jack 26 is actuatedto continually pivot the bucket 20 inwardly maintaining it in a levelposition.

The second important function which must be automatically provided toachieve automatic retraction of the backhoe boom is to correct for theattitude of the boom when it has completed the digging cycle. Theattitude of the boom is detected by the angle of pivotation in thevertical plane of the lift arm 16. The arm 16 may be in one of threepositions, that is, it may be too high, too low or at a correctposition. If, at the completion of the digging cycle, the arm 16 is in acorrect position for the retraction cycle, the lift arm position valve64 remains in the center position as shown in FIGURE 7 and no furthercorrection of the lift arm position is required. However, if the liftarm is too high, the lift arm position valve 64 is moved by cam 66 sothat a hydraulic pressure signal S6 is applied to conduit 102. Thepressure signal S6 serves two functions. First, it moves the high liftarm blocking valve 100 to the blocking position so that as long as thelift arm is too high the swing power valve 94 cannot be actuated. At thesame time signal S6 is applied to the lift power valve 34 to raise thelift arm. If the lift arm is too low at the initiation of the retractioncycle, signal S9 from lift arm position valve 64 is applied through liftshuttle valve 106 to produce signal S5 which in turn actuates the liftpower valve 34 to pivot the lift arm upwardly. Signal S9 also actuatesswing blocking valve 98 to prevent the boom from swinging until the lowposition of the lift arm is corrected.

If the lift arm position has been corrected by the time the crowd jackreaches the outer limit of its travel, signals S6 and S9 will not bepresent and valves 98 and 100 will be in the open position as shown.With these conditions when the crowd jack 24 reaches its outer limit thehigh crowd pressure actuates overload signal valve applying signal S8through the blocking valves 98 and 100 and the swing direction valve 96to actuate the swing power valve 94 to in turn actuate either the leftswing jack or the rig-ht swing jack 92 depending upon the setting of theswing direction selection valve 96. This initiates the swing of theboom. If the attitude of the lift arm has not been corrected when crowdjack 24 reaches its outer limit, that is, if the lift arm is stillpivoted too high or too low for the proper swing and dumping of thebucket, the signal S6 or 59 will continue to be applied until thecorrect attitude of the lift arm is achieved before swing initiationwill begin.

Thus, it can be seen that by the automatic digging cycle previouslydescribed and the automatic retraction cycle described with reference tothe system arrangement of FIGURE 7, the operator can achieve automaticdigging by merely pulling the crowd lever towards him and when theoperator determines to terminate the digging cycle,

which usually is when the crowd arm has reached the maximum inward pointor the bucket is filled, all the operator has to do to cause automaticretraction of the backhoe machine is to push the crowd lever forward tothe crowd out position. The leveling of the bucket, correcting of theattitude of the lift arm and the automatic initiating of the swing areall automatically accomplished by the system of this invention. When theboom has swung to the required position for dumping, the operator stopsthe swing by moving the manual crowd valve 28A back to the centerposition.

In the disclosed embodiment of the invention a novel system ofautomatically maintaining the bucket level during the retraction cycleis provided by means responsive to the crowd jack hydraulic pressure.Other methods of maintaining the bucket level during retraction includethe use of a pendulum or a gyroscopically actuated valve as well asother similar and equivalent devices.

Complete automatic backhoe digging machine To this point in thedescription the automatic operation of the digging cycle of the backhoemachine has been first described and then the automatic operation of adigging and retraction cycle system has been described. The third phaseof the invention, which will now be described, includes a completecomposite automatic backhoe machine.

As shown in FIGURE 1 and FIGURE 5, two cam operated valves, designated adump position cam valve 108 and a dig position cam valve 110, aremounted on the tractor 10 and are actuated by a dump position cam 112and a dig position cam 114. The cams 112 and 114 are tandem mounted andafiixed to the boom support base 116 to which the lift arm 16 isattached so that the cams 112 and 114 move with and indicate theposition in the horizontal plane of the boom 12 as it is moved by theswing cylinders 90 and 92. The function of the dump position cam valve108 and dig position cam valve 110 will be subsequently described.

In addition to the control valves which have been previously describedwith reference to the automatic digging system of this invention ofFIGURE 7, the total automatic system of this invention of FIGURE 8includes eleven additional hydraulically operated valves. The purposeand function of these will be described with reference to the operationof the composite circuit. These eleven additional hydraulically operatedvalves are as follows:

(1) a curl in looking valve 118 positioned between the curl signalshuttle valve 84 and the curl power valve 30; (2) a lift up detentlocking valve 120 positioned between the lift signal shuttle valve 106and the lift power valve 34;

(3) a left swing detent dig cycle blocking valve 122 positioned betweenthe swing direction valve 96A and the swing power valve 94;

(4) a right swing detent dig cycle blocking valve 124 positioned betweenthe swing direction valve 96A and the swing power valve 94;

(5) a lift shuttle valve 126 directing the down hydraulic signal to thelift power valve 34;

(6) a left swing shuttle valve 128 controlling signal input to the leftswinging side of the swing power valve 94;

(7) a right swing shuttle valve 130 controlling signal input into theright swing side of swing power valve 94;

(8) a curl empty overload signal valve 132 which monitors the hydraulicpressure of the out conduit of curl jack 26;

(9) a right swing blocking valve 134 positioned between the swingdirection valve 96A and the right of swing shuttle valve 130;

(10) a left swing blocking valve 136 positioned between the swingdirection valve 96A and the left swing shuttle valve 128; and

(11) a pilot operated crowd hold check valve 138 positioned in the outconduit 74 of the crowd jack 24. In addition to these hydraulicallycontrolled valves a manual digging attitude initiation selector valveprovides a means whereby the operator can select either one of twoconditions. In the first position, when the valve is closed, theautomatic cycle terminates when the back swing is completed with theboom extending over the ditch. In the second position, when the valve isopen, the boom automatically lowers into the ditch in digging attitudeat the end of the back swing.

In the complete automatic backhoe system of FIGURE 8, as compared withthe automatic digging and retraction system of FIGURE 7, swing directionValve 96A and curl power valve 30 are changed somewhat in type andfunction. A pilot check valve 146 and a check valve 148, comprising anand circuit, are added which function to actuate lift down shuttle valve126 upon the occurrence of signal S11 and S12.

The operation of complete automatic backhoe system The basic steps inthe operation of the automatic backhoe as illustrated in the diagram ofFIGURE 8 are as follows: I

(1) The operator selects the direction he wishes the backhoe to swing todump by moving the manual swing direction valve 96A. In addition, thedump position cam 112 and dig position cam 114 (see FIGURES 1 and 5) areset to correspond with the selected swing direction. The operator thenpositions the backhoe boom in position to start the digging cycle.

(2) The operator pulls crowd lever 70 (see FIGURE 4) back to actuatemanual valve 28A to initiate the digging cycle.

(3) The backhoe automatically executes the digging cycle as previouslydescribed.

(4) The operator arbitrarily decides when the digging cycle is completedand pushes crowd lever 70 forward to initiate the retraction cycle.

(5) The backhoe automatically retracts from the hole, maintaining thebucket in approximately level attitude, and initiates the swing cycle aspreviously described.

(6) The backhoe automatically swings until it reaches the preselecteddump position as established by the dump position cam 112.

(7) The'backhoe swing stops and the load carried by the bucket isautomatically dumped.

(8) The dumping completed, the boom automatically swings back to thepreselected dig position as established by dump position cam 112 (seeFIGURES 1 and 5) and automatically lowers into the hole.

(9) The operator pulls the crowd lever 70 back to begin a new diggingcycle.

Thus, all that is required of the operator is that he pull the crowdlever back to begin the digging cycle, push the crowd lever forward whenthe bucket is full to cause the boom to begin automatic retraction,swing, dump and reswing to digging position, and then pull the crowdlever back to begin a new cycle.

The function of the composite automatic control system of this inventionwill now be described. As previously mentioned, after positioning theboom of the backhoe in digging attitude, the operator actuates themanual control valve 28A so as to cause hydraulic pressure in conduit38. At the same time conduit 74 is tanked. Pressure in conduit 38 passesthrough pilot check valves 52 and 56 to extend the crowd jack 24 forcingthe crowd arm inwardly and into the ground. The same fluid pressure alsoresets the curl-in detent blocking Valve 118, lift-up detent blockingvalve 120, lift swing detent dig cycle blocking valve 122, and rightswing detent dig cycle blocking valve 124. Overload signalvalve 4Omonitors the working pressure in the crowd line 38. The overload signalvalve 40, as well as the other overload signal valves in this invention,are supplied from a hydraulic signal pressure force by conduit 42.

When the working pressure in the crowd line 38 builds to a preselectedlevel, the crowd overload signal valve 40 is actuated producing ahydraulic signal S1 which proceeds through the curl signal shuttle valve84 and conduit 60 to the curl-in detent blocking valve 118 to producesignal S2 which pilots the curl power valve 30. The curl power valve 30as previously described serves as a directional power valve for the curljack 26. Hydraulic flow in line 44 through pilot check valves 54 and 58extends the curl jack 26 to curl inward the backhoe bucket 20 (seeFIGURE 1). When the signal S2 pilots curl power valve 30 the pressure inthe backhoe system will reduce due to the lack of resistance encountered'by the curl jack. Therefore, pilot check valve 52 in the crowd-inconduit 38 looks the high pressure which has activated the overloadsignal valve 40 in the crowd conduit. This means that the overloadpressure condition on the crowd jack must be actually relieved in thejack and not by reduction in system pressure. Pilot check valve 56serves as a low pass filter for the crowd overload signal valve 40. Thisprevents shock waves which might be generated in the crowd pack 24 fromactuating the signal valve 40.

Curl overload signal valve 46 monitors working pressure in the curl jack26 and produces a hydraulic signal S3 when the curl signal pressurereaches a preselected overload condition. Signal S3 is normally blockedby pilot operated check valve 50 except when this valve has beenactuated by signal S1. Thus, the pilot check valve 50 functions, withcheck valve 51, as an and gate to generate a signal S4 when both signalsS1 and S3 are present. Signal S4 in conduit 60 precedes through the liftsignal shuttle valve 186 and the lift-up detent blocking valve 120 toproduce signal S5 which pilots the lift power valve 34. As previouslyindicated, the lift power valve 34 serves as the directional power valvefor the lift jack 22. When signal S5 is present, conduit 62 ispressurized causing the lift jack 22 to extend pivoting the lift armupwardly.

When the lift jack 22 is being extended, pilot check valve 54 in thecurl line 44 isolates the curl overload signal in the same manner aspreviously described with reference to valve 56. Pilot operated checkvalve 58 serves as a low pass filter for the curl overload signal valve46.

If the overload condition on the curl jack 26 is relieved by theextension of lift jack 22, signal S3 in conduit 48 is lost and the liftpower valve 34 is returned to the center position. The crowd and curljacks 24 and 26 are still actuated and performing the digging action. Ifthe overload condition on the crowd jack 24 or on both the crowd jack 24and the curl jack 26 are relieved by the extension of the lift jack 22,both the lift and curl power valves 34 and 30 are returned to blockcenter position leaving only the crowd jack 24 actuated and attemptingto dig. The backhoe performs the digging cycle by continuously repeatedaction of the events just described.

When the operator decides that the digging cycle is completed, hereverses the crowd lever 70 (see FIGURE 4) which reverses the manualcrowd valve 28A. This action pressurizes conduits 74 and tanks conduit38. If the operator desires automatic retraction, selection valve 72 ispositioned in the open position as shown in FIGURE 8. Automaticretraction valve 68 is operated when the crowd lever 70 is pushedforward (see FIG- URE 4). Physical action of the automaticretractionswing circuit which results from reversal of the crowd leveris the next step in any complete automatic operation of the backhoe ofthis invention.

Upon initiation of the retraction cycle, the lift arm 16 of the boom canbe in one of three positions. These positions are (l) the left arm 16(see FIGURE 1) is too high for swinging at the end of the digging cycle;(2) the left arm 16 is too low for swinging at the end of the diggingcycle; and (3) the lift arm 16 is in correct position for swinging atthe end of the digging cycle.

The correct position for swinging is preselected by positioning the leftposition cam 66 (see FIGURE 6) which operates the lift positiondetection valve 64.

When the position of the lift arm 16. is too high, lift position valve64 gives a signal S6 in conduit 102 which signal passes through the liftdown shuttle valve 126 to actuate the lift power valve 34, providingfluid pressure in conduit 142. This tends to drive the lift arm 16 andthereby the boom down until signal S6 from the lift position valve 64 iseliminated. While the boom is moving downward, the crowd jack 24 isbeing actuated, thus raising the crowd arm 18 (see FIGURE 1) from thehole. Overload signal valves 78 and 80 monitor the pressure existing inthe crowd-out line conduit 74 and in conduit 76. The pressure overloadsignal valve 78 is set at a relatively low threshold pressure to providebucket leveling action as the backhoe boom is being withdrawn from thehole. The action of this valve, which has been previously described,provides signal S7 which passes through the curl signal block valve 88,by way of conduit 82, through the curl signal shuttle valve 84 and thecurl-in detent blocking valve 118 to actuate curl power valve 30. As thecrowd arm moves outward, the pressure in the crowd jack out conduit 74increases which increased pressure continues to actuate the curl powervalve 30 extending the curl jack 26 so that the leveling action iscontinuously repeated in a stepwise manner as the crowd arm proceedsoutward-1y main taining the bucket in substantially level position. Thecrowd arm 18 continues out until it reaches the limit of travel whichproduces a high pressure rise in crowd out conduit 74, thereby inconduit 76, which actuates the high pressure overload signal valve 80producing signal S8. The threshold setting of the high pressure signalvalve 80 is substantially greater than that of the overload signal valve78 to insure that valve 80 will not actuate until the crowd arm reachesits limit of travel. Signal S8 actuates the curl signal block valve 88which tanks signal S7 and allows curl power valve 30 to return toblocked neutral position. Signal S8 also passes through low lift armblocking valve 98, high lift arm blocking valve 100, swing directionvalve 96A and initiates the automatic swing cycle. If the boom is toohigh or too low when the crowd jack reaches its outer limit, the signalS8 will be blocked by either blocking valve 98 or 100 so that the signalS8 cannot pass through to initiate the swinging cycle. When the boom isin the correct position for swinging, as will be indicated by the centerposition of the lift position valve 64, there will be no signal toactuate the blocking valves 98 and 100 to prevent the signal S8 frompassing through.

If the boom lift arm 16 happens to be in the correct swing position atthe end of the digging cycle, the circuit action is the same aspreviously described with the exception that the lift arm remainsstationary while the crowd arm 18 raises to swing position. When thecrowd arm is in position, signal S8 is produced and passes through theblocking valves 98 and 100 to initiate the swinging cycle.

In the case where the lift arm 16 is too low at the end of the diggingcycle, the sequence of action is as follows: (1) The operator aspreviously described pushes the crowd valve 28A to initiate retraction,and pressure is thereby direction applied to the crowd jack 24 throughconduit 74 tending to force the crowd arm 18 out. (2) Signal valves 78and 80 monitor the pressure in the crowd out line. (3) The lift positioncam valve 64 is in position providing signal S9 in conduit 104. SignalS9 passes through the lift signal shuttle valve 106 and the lift-updetent blocking valve to pilot the lift power valve 34 to cause the boomto raise and to swing into position. However, the pressure required toraise the lift arm is much greater than the pressure required to drivethe crowd out, therefore, the lift arm 16 will not raise until the crowdarm 18 has reached the limit of travel. Pilot check valve 144 in conduit62 retains the lift arm in pbsition until the crowd arm 18 has reachedthe outward extremity of its travel. (4) As crowd arm 18 proceedsoutward, signal valve 78 monrtors the crowd pressure in order to levelthe bucket as previously described. (5 When the crowd jack 24 reachesits limit of travel, signal valve 80 is actuated. At this time pressurebuild up in the system will become sufficient to raise the lift arm 16into swing position, allowing signal S8 to pass valves 98 and 100 toinitiate the automatic swing cycle.

As previously mentioned, the operator has the option of making thebackhoe boom swing to the left or right by positioning the swingdirection valve 96A. The dump position cam valve 108 and the digposition cam valve 110 are swing position detection valves and areadjusted according to the direction the operator desires to swing. Whenthe swing direction selection valve 96A is positioned as shown in FIGURE8, the backhoe boom will swing to the left with the dump position camvalve 108 detecting the position at which to dump the load and the digposition cam valve 110 detecting the position selected to lower thebackhoe boom into the hole for another digging pass. If the swingdirection valve 96A is shifted to its other position, the backhoe boomwill swing right with the valve 110 serving to detect the dump positionand the valve 108 serving to detect the dig location. Thus, it can beseen that the cam valves 108 and 110 must be physically adjusted tocorrespond with the shifting of the swing direction valve 96A.

With the swing direction valve 96A positioned as shown in FIGURE 8,signal S8 can pass through valves 96A, left swing dig cycle blockingvalve 122, the left swing shuttle valve 128 to pilot the swing powervalve 94. This causes fluid pressure to flow into the left swing jack90, causing the backhoe boom to begin its swing cycle.

The dump position cam valve 108 actuates when the backhoe boom hasreached the desired du-rnp position. Actuation of the dump position camvalve 108 produces a signal S10 which passes through the swing directionvalve 96A and sets the curl in detent blocking valve 118 and the lift updetent blocking valve 120, and pilots the curl power valve 30 to causethe bucket 20 (see FIGURE 1) to be pivoted out or open to dump the load.At the same time the signal S10 sets the left swing detent dig cycleblocking valve 122 which causes the pilot signal to the swing powervalve 94 to be tanked, returning the valve 94 to the center positionstopping the boom from further swinging. Pilot operated crowd hold checkvalve 138 prevents the crowd arm from falling when the load is beingdumped. This is necessary because of the'low pressure existing in thehydraulic system during load dumping.

Curl empty overload signal valve 132 produces a signal $11 when the curljack 26 reaches the end of its downward travel. This signifies that thedumping action is completed and the backhoe is ready to swing back intodigging location. Signal S11 passes through the swing direction valve96A, the right swing blocking valve 134, the right swing shuttle 130, topilot the swing power valve 94 so as to make the backhoe boom swing backto digging location. Dig position cam valve 110 actuates when thebackhoe boom has swung to the digging position. The actuation of the digposition ca m valve 110 produces a signal S12 which actuates the rightswing blocking valve 134 stopping fu'rther swinging action of the boom.Signal S12 also passes through the swing direction valve 96A, the manualdigging attitude initiation selector valve 140 and pilot valve 146 topass signal S11 to produce signal S13. Signal S13 passes through thelift down shuttle valve 126 to pilot the lift jack power valve 34. Thisaction causes the lift jack 22 to be actuated so as to cause the backhoeboom to lower into the hole for another operation cycle. When theoperator observes that the boom is lowered far enough into the hole, hereverses the crowd lever 70 (see FIG- URE 4) and a new digging cyclebegins.

A manual dig attitude initiation selector valve 140 lets 14 the operatordeteninine if he wants the backhoe boom to automatically lower into thehole when it returns from the dumping cycle or if he wants the boom toautomatically stop and be manually located into digging position.

The pilot operated check valve 146 in conjunction with a check valve 148for-ms an and circuit so that signal S11 and signal S12 produce signalS13 which passes through the lift down shuttle valve 126 to pilot thelift power valve 34 to lower the boom into position. If valve isclose-d, signal S12 and thereby signal S13 is blocked so the lift jack22 will have to be actuated manually to lower the boom.

By switching the swing direction valve 96A and repositioning the dumpposition cam 112 and the dig position cam 114 so as to exchange thefunctional rolls of valves 108 and 110, the backhoe boom is caused toswing to the right and the circuit action duplicates that described forthe left swing action.

In FIGURE 8 the dotted line represents conduits which carry signals. Thesolid line represents conduits which carry hydraulic fluid pressure usedin the actuation of the jacks which control the components of thebackhoe boom.

A type of valve which is specifically adaptable to function as overloadsignal valves 40, 46, 80, 82, and 132 in the system of this invention isdescribed in our copending patent application Ser. No. 482,829 entitledHydraulic Signal Valve.

In the working embodiment of the systems of this inven tion, it isdesirable that flow control valves be utilized in certain instances toslow the action of the jacks. In addition, devices to cushion thestopping of the swing cylinders are desired. Since such devices are notbasic to the systems of this invention, they have not been shown.

While the invention has been described with a certain degree ofparticularity, it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure.

What is claimed:

1. A back hoe machine comprising:

(a) a tractor;

(b) a boom consisting of (l) a liftarm pivoted at one end to saidtractor,

(2) a crowd arm pivoted at one end to the other end of said lift arm,and

(3) a bucket pivoted to the other end of said crowd arm;

(0) a double acting hydraulic lift jack pivotallyaflixed at one end tosaid tractor and at the other end to said lift arm whereby said lift armis pivotally positioned relative to said tractor to increased ordecreased digging attitude;

'(d) a double acting hydraulic crowd jack pivotally affixed at one endto said lift arm and at the'other end to said crowd arm whereby saidcrowd arm is pivotally positioned relative to said lift arm to increasedor decreased digging attitude;

(e) a double acting hydraulic curl jack pivotally aflixed at one end tosaid crowd arm and at the other end to said bucket whereby said bucketis pivotally'positioned relative to said crowd arm to increased ordecreased digging attitude; I

(f) a source of hydraulic pressure carried by said tractor; 1

(g) a hydraulically operated lift power valve controlling hydraulicfiuid flow to said lift jack;

(h) a hydraulically operated curl power valve controlling hydraulicfluid flow to said curl jack;

(i) a crowd overload signal valve in communication with and sensitive tothe hydraulic pressure in said crowd jack and providing hydraulic signalwhen the pressure in said crowd jack exceeds a preselected level as saidcrowd jack moves said crowd arm to increased digging attitude, saidhydraulic signal coupled to said curl power valve whereby overload in 15 said crowd overload signal valve actuates said curl power valve tocontrol said curl jack to decrease the digging attitude of said bucket;

(j) a curl overload signal valve in communication with and responsive tothe hydraulic pressure in said curl jack and actuating to provide ahydraulic signal when the pressure in said curl jack exceeds apreselected level as said curl jack pivots said bucket to increaseddigging attitude; and

(k) a pilot operated valve actuated by hydraulic signal from said crowdoverload signal valve and said curl overload signal valve providing ahydraulic lift control signal upon occurrence of said two signals, suchlift control signal actuating said lift power valve to control said liftjack to decrease the digging attitude of said lift arm.

2. A back hoe machine according to claim 1 including means of tankingsaid lift control hydraulic signal when said curl overload signal valveis unactuated.

3. With a back hoe machine including a tractor,

a boom consisting of a lift arm pivoted at one end to said tractor,

a crowd arm pivoted at one end to the other end of said lift arm, and

a bucket pivoted to the other end of said crowd arm,

a hydraulic lift jack pivotally affixed at one end to said tractor andat the other end to said lift arm whereby said lift arm is pivotallypositioned relative to said tractor to increased or decreased diggingattitude,

hydraulic crowd jack pivotally affixed at one end to said lift arm andat the other end to said crowd arm whereby said crowd arm is pivotallypositioned relative to said lift arm to increased or decreased diggingattitude,

a double acting hydraulic curl jack pivotally afiixed at one end to saidcrowd arm and at the other end to said bucket whereby said bucket ispivotally positioned relative to said crowd arm to increased ordecreased digging attitude, and

a source of hydraulic pressure carried by said tractor, and means ofdirecting hydraulic pressure to said crowd jack, the improvementproviding means of automatically controlling the pivotation of said liftarm, crowd arm and bucket to achieve automatic digging, the improvementcomprising:

a hydraulically operated lift power valve controlling hydraulic fluidflow to said lift jack;

a hydraulically operated curl power valve controlling hydraulic fluidflow to said curl jack;

a crowd overload signal valve in communication with and responsive tothe hydraulic pressure in said crowd jack and providing a hydraulicsignal when the pressure in said crowd jack exceeds a preselected levelas said crowd jack moves said crowd arm to increased digging attitude,said hydraulic signal cou pled to said curl power valve whereby overloadit: said crowd overload signal valve actuates said curl power valve tocontrol said curl jack to decrease the digging attitude of said bucket;

a curl overload signal valve in communication with and responsive to thehydraulic pressure in said curl jack and actuating to a hydraulic signalwhen the pres sure in said curl jack exceeds a preselected level as saidcurl jack pivots said bucket to decreased digging attitude; and

a pilot operated valve actuated by hydraulic signal from said crowdoverload signal valve and said curl overload signal valve providing ahydraulic lift control signal upon occurrence of said two signals, suchlift control signal actuating said lift power valve to control said liftjack to decrease the digging attitude of said lift arm.

15 4. The improvement of claim 3 including means of tanking said liftcontrol hydraulic signal when said curl overload signal valve isunactuated.

5. With a back hoe machine including a tractor,

a boom consisting of a lift arm pivoted at one end to said tractor,

a crowd arm pivoted at one end to the other end of said lift arm, and

a bucket pivoted to the other end of said crowd arm,

a double acting hydraulic lift jack having an up port and a down port,the jack pivotally affixed at one end to said tractor and at the otherend to said lift arm whereby said lift arm is pivotally positionedrelative to said tractor to increased or decreased digging attitude,

a double acting hydraulic crowd jack having an in and an out port, thejack pivotally affixed at one end to said lift arm and at the other endto said crowd arm whereby said crowd arm is pivotally positionedrelative to said lift arm to increased or decreased digging attitude,

a double acting hydraulic curl jack having an in and an out port, thejack pivotally affixed at one end to said crowd arm and at the other endto said bucket whereby said bucket is pivotally positioned relative tosaid crowd arm to increased or decreased digging attitude,

a source of hydraulic pressure carried by said tractor,

a manual lift valve controlling fluid communication between saidpressure source and said lift jack,

a manual crowd valve controlling fluid communication betlween saidpressure source and said crowd jack, an

a manual curl valve controlling fluid communication between saidpressure source and said curl jack, the improvement providing means ofautomatically controlling the pivotation of said lift arm, crowd arm andbucket to achieve automatic digging, the improvement comprising:

a pilot operated hydraulic lift power valve paralleling said manual liftvalve;

a pilot operated hydraulic curl power valve paralleling said manual curlvalve;

a crowd overload signal valve in communication with and responsive tothe hydraulic pressure in said jack and providing a hydraulic crowdoverload signal when the pressure in said crowd jack exceeds apreselected level;

means communicating said crowd overload signal to pilot said curl powervalve to actuate said curl jack to decrease the digging attitude of saidbucket;

a curl overload signal valve in communication with and responsive to thepressure in said curl jack and providing a hydraulic curl overloadsignal when the pressure in said curl jack exceeds a preselected level;

a pilot operated check valve having an inlet, an outlet and a controlport;

means communicating said crowd overload signal with one of the saidinlet and control ports of said pilot operated check valve;

means communicating the other of said inlet and control ports of saidcurl overload signal with pilot operated check valves whereby ahydraulic lift control signal is provided at said outlet port upon thesimultaneous occurrence of said crowd and curl overload signals; and

means communicating said lift control signal to said lift power valvepilot port to actuate said lift jack to pivot said lift arm towardsdecreased digging attitude when said crowd jack and said curl jack areoverl ade 6. The improvement of claim '5 including means of dumping saidlift control signal when said curl overload signal valve is unactuated.

7. The improvement of claim including a first and second pilot operatedcheck valve in series with said crowd jack in port, each check valvepiloted by hydraulic pressure in said crowd jack out port, said crowdoverload signal valve communicating with said crowd jack intermediatesaid check valves whereby overload hydraulic pressure in said crowd jackapplied to said crowd overload signal valve is isolated from reductionsin pressure in said source of hydraulic pressure.

8. The improvement of claim 5 including a first and second seriesedcheck valve between said curl jack in port and said curl power valve,said curl overload signal valve communicating with the pressure in saidcrowd jack intermediate said seriesed check valve whereby the pressureactuating said curl overload signal valve is isolated from reductions inpressure in said source of hydraulic pressure.

9. With a back hoe machine including a tractor,

a boom consisting of a lift arm pivoted at one end to said tractor,

a crowd arm pivoted at one end to the other end of said lift arm, and

a bucket pivoted to the other end of said crowd arm,

a hydraulic lift jack pivotally aflixed at one end to said tractor andat the other end to said lift arm whereby said lift arm is pivotallypositioned relative to said tractor to increased or decreased diggingattitude, hydraulic crowd jack pivotally aflixed at one end to said liftarm and at the other end to said crowd arm whereby said crowd arm ispivotally positioned relative to said lift arm to increased or decreaseddigging attitude,

a hydraulic curl jack pivotally aflixed at one end to said crowd arm andat the other end to said bucket whereby said bucket is pivotallypositioned-relative to said crowd arm increased or decreased diggingattitude,

source of hydraulic pressure carried by said tractor,

a manual lift valve controlling fluid communication between saidpressure source and said liftjack,

a manual crowd valve controlling fluid communication between saidpressure source and'said crowd jack, and

a manual curl valve controlling fluid communication between saidpressure source and said curl jack, the improvement comprising:

a hydraulically operated lift power valve paralleling said manual liftvalve;

a hydraulically operated curl power valve paralleling said manual curlvalve;

means responsive to overload pressure in said crowd jack of actuatingsaid curl power valve to cause pivotation of said bucket to decreaseddigging attitude; and

means responsive to the simultaneous overload pressure in said crowdjack and said curl jack to cause pivotation of said lift arm todecreased digging attitude.

10. A back hoe machine comprising:

a tractor,

a boom consisting of v a lift arm pivoted at one end to said tractor,

a crowd arm pivoted at one end to the other end of said lift arm, and

a bucket pivoted to the other end of said crowd arm,

a double acting hydraulic lift jack pivotally affixed at one end to saidtractor and at the other end to said li-ft arm whereby said lift arm ispivotally positioned relative to said tractor to increased or decreaseddigging attitude,

a double acting hydraulic crowd jack pivotally aflixed at one end tosaid lift arm and at the other end to said crowd arm whereby said crowdarm is pivotally postioned relative to said lift arm to increased ordecreased digging attitude,

a double acting hydraulic curl jack pivotally aflixed atone end to saidcrowd arm and at the other end to said bucket whereby said bucket ispivotally positioned relative to said crowd arm increased or decreaseddigging attitude,

a source of hydraulic pressure carried by said tractor,

a manual lift valve controlling fluid communication between saidpressure source and said lift jack,

a'manual crowd valve controlling fluid communication between saidpressure source and said crowd jack,

a manual curl valve controlling fluid communication between saidpressure source and said curl jack,

a hydraulically operated four way blocked center curl power valveparalleling said manual curl valve, and

means responsive to overload pressure in said crowd jack of actuatingsaid curl power valve to cause inward pivotation of said bucket as saidcrowd arm is pivoted outwardly whereby said bucket is automaticallymaintained substantially level as said crowd arm is extended outwardly.

. 11. With a back hoe machine including a tractor, a boom consisting ofa lift arm affixed at one end to said tractor, said lift arm aflixed topivot in both the horizontal [and vertical plane relative to saidtractor, a crowd arm pivoted at one end to the other en of said liftarm, and a bucket pivoted to the other end of said crowd arm,

a double acting hydraulic crowd jack having an in and an out port, thisjack pivotally aflixed at one end to said lift arm and at the other endto said crowd arm whereby said crowd arm is pivotally positioned in thevertical relative to said lift arm,

a hydraulic left swing jack having one end pivotally aflixed to saidtractor and the other end to said boom whereby said boom is pivotallypositioned in the horizontal plane in the direction left relative tosaid tractor, Y f I v a hydraulic right swing jack having one endpivotally afiixed to said tractor andthe other end to said boom wherebysaid boom is pivotally positioned in the horizontal plane in thedirection rightr'elative to said tractor, and I v a source of hydraulicpressure carried by said tractor, the improvement comprising:

a hydraulically operated swing power valve controlling fluidcommunication between said pressure source I v and said left and rightswing jacks,,said swing power valve having a right swing pilot port anda leftswing pilot port; a manually operated swing direction valveselectably 7 providing fluid communication between said swing powervalve andione or the other of said left and right swing jacks;

-means responsiveto overload pressure in 'said out port of said crowdjack of providing a hydraulic signal when said crowd jack reaches itsouter limit of travel; and

a manually positioned swing direction valve selectably providingcommunication between said crowd overload pressure responsive means andone or the other of said left and right swing ports of said swing powervalve whereby said boom automatically swings when said crowd jackreaches its outer limit of travel.

12. With a back hoe machine including i a tractor,

a boom consisting of a lift arm aflixed at one end to said tractor, said19 lift arm affixed to pivot in the vertical plane relative to saidtractor, a crowd arm pivoted at one end to the other end of said liftarm, and a bucket pivoted to the other end of said crowd arm,

a double acting hydraulic crowd jack having an in and an out port, thisjack pivotally aflixed at one end to said lift arm and at the other endto said crowd arm whereby said crowd arm is pivotally positioned in thevertical relative to said lift arm, and

a source of hydraulic pressure carried by said tractor,

the improvement comprising:

a hydraulically operated lift power valve controlling fluidcommunication between said pressure source and said crowd jack;

I a lift position detector valve afiixed to said tractor and actuated bysaid lift arm providing a first hydraulic signal when said lift arm ispivoted in the vertical plane above a selected angle relative to saidtractor and a second hydraulic signal when said lift arm is pivoted inthe veritcal plane below the selected angle relative to said tractor,and no signal when the said lift arm is pivoted in the selected angle;and

means connecting said lift position detector valve to said lift powervalve whereby said first hydraulic signal of said lift position detectorvalve actuates said lift powervalve to lower said lift armand saidsecond hydraulic signal of said lift position detector valve actuatessaid lift power valve to raise said lift arm.

13. A back hoe machine according to claim 12 wherein said lift positiondetector valve communicates with said crowd .jack out port whereby saidfirst and second hydraulic signals are provided only when hydraulicpressure is applied to said crowd jack out port.

14. With a back hoe machine including a tractor,

- a boom consisting of a lift arm affixed at one end to said tractor,said lift arm affixed to pivot in both the horizontal and vertical planerelative to said tractor,

a crowd arm pivoted at one end to the other end of said lift arm, and

a bucket pivoted to the other end of said crowd arm,

a double acting hydraulic crowd jack having an in and an out port,thisjack pivotally affixed at one end to said lift arm and at the otherend to said crowd arm whereby said crowd arm is pivotally positioned inthe vertical relative to said lift arm,

a hydraulic left swing jack having one end pivotally affixed to saidtractor and the other end to said boom whereby said boom is pivotallypositioned in the horizontal plane in the direction left relative tosaid tractor,

a hydraulic right swing jack having one end pivotally affixed to saidtractor and the other end to said boom whereby said boom is pivotallypositioned in the horizontal plane in the direction right relative tosaid tractor, and

a source of hydraulic pressure carried by said tractor,

the improvement comprising:

a hydraulically operated swing power valve controlling fluidcommunication between said pressure source and said left and right swingjacks, said swing power valve having a right swing pilot port and a leftswing pilot port;

a manually operated swing direction valve selectably providing fluidcommunication between said swing power valve and one or the other ofsaid left and right swing jacks; a

means responsive to overload pressure in said out port of said crowdjack of providing a hydraulic signal when said crowd jack reaches itsouter limit of travel;

a manually positioned swing direction valve selectably providingcommunication between said crowd overload pressure responsive means andone or the other of aid left and right swing ports of said swing powervalve whereby said boom automatically swings when said crowd jackreaches its outer limit of travel;

a lift position detector valve affixed to said tractor and actuated bysaid lift arm providing a first hydraulic signal when said lift arm ispivoted in the vertical plane above a selected angle relative to saidtractor and a second hydraulic signal when said lift arm is pivoted inthe vertical plane below the selected angle 'relative to said tractor,and no signal when the said lift arm is pivoted in the selected angle;

means connecting said lift position detector valve to said lift powervalve whereby said first hydraulic signal of said lift position detectorvalve actuates said lift power valve to lower said lift arm and saidsecond hydraulic signal of said lift position detector valve actuatessaid lift power valve to raise said lift arm; and

a first and a second pilot operated normally open swing blocking valve,each of said valves having a pilot port, said valves in seriesconnection between said swing power valve and said means responsive topressure in said out port of said crowd jack, said pilot port of one ofsaid valves connected to receive the first signal of said lift positiondetector valve, said pilot port of the other of said valves connected toreceive the second signal of said lift position detector valve, wherebyeither signal from said lift position detector valve blocks one of saidswing blocking valves.

15. With a back hoe machine including a tractor, a boom consisting of alift arm pivoted at one end to said tractor, a crowd arm pivoted at oneend to the other end of said lift arm and a bucket pivoted to the otherend of said crowd arm, a hydraulic crowd jack pivotally aflixed at oneend to said lift arm and at the other end to said crowd arm, forpivotation of said crowd arm, a hydraulic curl jack pivotally affixed atone end to said crowd arm and at the other end to said bucket, forpivotation of said bucket, a source of hydraulic pressure and means ofselectably directing hydraulic pressure to said crowd jack and said curljack, the improvement providing means of automatically maintaining saidbucket level as said crowd arm is pivoted outwardly, the improvementcomprising:

a hydraulically actuated curl power valve controllably directingpressure from said hydraulic source to said curl jack;

an overload signal valve in communication with and responsive tohydraulic pressure in said crowd jack and providing a hydraulic signalresponsive to the pressure increases as said crowd jack pivots saidcrowd arm outwardly; and

means coupling said hydraulic signal from said overload signal valve tosaid curl power valve whereby said curl power valve is actuated toactuate said curl jack to pivot said bucket inwardly in response toincreased pressure in said crowd jack as said crowd arm is pivotedoutwardly.

16. A back hoe machine for mounting on a tractor, in-

cluding:

a boom support base adapted to be mounted for horizontal swingingmovement on the tractor;

a boom consisting of a lift arm pivoted at one end to the boom supportbase;

a crowd arm pivoted at one end to the other end of said lift arm; and

a bucket pivoted to the other end of said crowd arm;

a hydraulic lift jack pivotally aflixed at one end to said boom supportbase and at the other end to said lift arm whereby said lift arm ispivotally positioned relative to said tractor to increased or decreaseddigging attitude;

a hydraulic crowd jack pivotally affixed at one end to said lift arm andat the other end to said crowd arm whereby said crowd arm is pivotallypositioned relative to said lift arm to increased or decreased diggingattitude;

a hydraulic curl jack pivotally aflixed at one end to said crowd arm andat the other end to said bucket whereby said bucket is pivotallypositioned relative to said crowd arm increased or decreased diggingattitude;

a source of hydraulic pressure carried by said tractor;

a manual lift valve controlling fluid communication between saidpressure source and said lift jack;

a manual crowd valve controlling fluid communication between saidpressure source and said crowd jack; and

a manual curl valve controlling fluid communication between saidpressure source and said curl jack, the improvement comprising:

means responsive to overload pressure in said crowd jack for directingfluid under pressure to said curl jack to cause pivoting of said bucketto decreased digging attitude, and means responsive to simultaneousoverload pressure in said crowd jack and said curl jack for directingfluid under pressure to said lift jack to cause pivoting of said liftarm to decreased digging attitude. 17. A back hoe machine for mountingon a tractor, in-

cluding:

arm whereby said lift arm is pivotally positioned relative to saidtractor to increased or decreased digging attitude;

a hydraulic crowd jack pivotally afiixed at one end to said lift arm andat the other end to said crowd arm whereby said crowd arm is pivotallypositioned relative to said lift arm to increased or decreased diggingattitude;

a hydraulic curl jack pivotally affixed at one end to said crowd arm andat the other end to said bucket whereby said bucket is pivotallypositioned relative to said crowd arm increased or decreased diggingattitude;

a source of hydraulic pressure carried by said tractor;

a lift valve controlling fluid communication between said pressuresource and said lift jack; a crowd valve controlling fluid communicationbetween said pressure source and said crowd jack; and a curl valvecontrolling fluid communication between said pressure source and saidcurl jack, the improvement comprising:

means responsive to overload pressure in said crowd jack for actuatingsaid crowd valve to direct fluid under pressure to said curl jack tocause pivoting of said bucket to decreased digging attitude; and meansresponsive to simultaneous overload pressure in said crowd jack and saidcurl jack for ac- 22 tivating said lift valve to direct fluid underpressure to said lift jack to cause pivoting of said lift arm todecreased digging attitude.

18. A barck hoe machine as claimed in claim 17, having means fordirecting fluid under pressure to said crowd jack to cause outwardpivoting of said crowd arm and means responsive to said pivotingmovement of the crowd arm to direct fluid under pressure to said curljack to cause pivoting of the bucket to maintain it in substantiallylevel position.

19. A back hoe machine as claimed in claim 18 having means for sensingheight of the lift arm and directing fluid under pressure to the liftcylinder if required to raise the lift arm to retract the bucket fromthe excavation.

20. In a back hoe for mounting on a tractor, said back hoe comprising:

a boom support base mounted for horizontal swinging movement on an endof the tractor;

a boom consisting of:

20 a lift arm having an end pivotally mounted for vertical swingingmovement on the boom support base;

a crowd arm having an end pivotally mounted for vertical swingingmovement on the other end of the lift arm; and

a bucket pivotally mounted for vertical swinging movement on the otherend of the crowd arm; a hydraulic lift jack extending between the liftarm and boom support base for raising and lowering the lift arm todecreased and increased digging attitudes, respectively,

a hydraulic crowd jack extending between the lift arm and crowd arm forpivotally positioning the crowd arm to increased and decreased diggingattitude;

a hydraulic swing cylinder connected between the tractor and the boomsupport base for pivotally positioning said boom support base;

a hydraulic curl jack connected between the crowd arm and the bucket forpivotally positioning the bucket to increased and decreased diggingattitude;

a source of hydraulic fluid under pressure associated with the back hoe;

a lift valve controlling flow of fluid under pressure to said lift jack;

a crowd valve controlling flow of fluid under pressure to said crowdjack; and

a curl valve controlling flow of fluid under pressure to said curl jack,the improvement comprising:

means for directing fluid under pressure to said crowd jack to causeoutward pivoting of said crowd arm towards decreased digging attitude;and

means responsive to said pivoting movement of the crowd arm to directfluid under pressure to said curl jack to cause pivoting of the bucketto maintain it in substantially level position.

21. In a back hoe as claimed in claim 20, means for sensing height ofthe lift arm and directing fluid under pressure to the lift cylinder ifrequired to raise the lift ar to retract the bucket from the excavation.

22. In a back hoe as claimed in claim 21, means responsive topositioning of the lift arm and crowd arm so as to retract the bucketfrom the excavation for directing fluid under pressure to the swingcylinder to institute swing of the back hoe from above the excavation.

No references cited.

HUGO O, SCI-IUL-Z, Primary Examiner,

1. A BACK HOE MACHINE COMPRISING: (A) A TRACTOR; (B) A BOOM CONSISTINGOF (1) A LIFT ARM PIVOTED AT ONE END TO SAID TRACTOR, (2) A CROWD ARMPIVOTED AT ONE END TO THE OTHER END OF SAID LIFT ARM, AND (3) A BUCKETPIVOTED TO THE OTHER END OF SAID CROWD ARM; (C) A DOUBLE ACTINGHYDRAULIC LIFT JACK PIVOTALLY AFFIXED AT ONE END TO SAID TRACTOR AND ATTHE OTHER END TO SAID LIFT ARM WHEREBY SAID LIFT ARM IS PIVOTALLYPOSITIONED RELATIVE TO SAID TRACTOR TO INCREASED OR DECREASED DIGGINGATTITUDE; (D) A DOUBLE ACTING HYDRAULIC CROWD JACK PIVOTALLY AFFIXED ATONE END TO SAID LIFT ARM AND AT THE OTHER END TO SAID CROWD ARM WHEREBYSAID CROWD ARM IS PIVOTALLY POSITIONED RELATIVE TO SAID LIFT ARM TOINCREASED OR DECREASED DIGGING ATTITUDE; (E) A DOUBLE ACTING HYDRAULICCURL JACK PIVOTALLY AFFIXED AT ONE END TO SAID CROWD ARM AND AT THEOTHER END TO SAID BUCKET WHEREBY SAID BUCKET IS PIVOTALLY POSITIONEDRELATIVE TO SAID CROWD ARM TO INCREASED OR DECREASED DIGGING ATTITUDE;(F) A SOURCE OF HYDRAULIC PRESSURE CARRIED BY SAID TRACTOR; (G) AHYDRAULICALLY OPERATED LIFT POWER VALVE CONTROLLING HYDRAULIC FLUID FLOWTO SAID LIFT JACK; (H) A HYDRAULICALLY OPERATED CURL POWER VALVECONTROLLING HYDRAULIC FLUID FLOW TO SAID CURL JACK;